❯ ❯ Itch

As the journal Clinical & Experimental Allergy explains, "itch, or pruritus, can be defined as an unpleasant sensation that evokes the desire to scratch. [C]hronic itch originates from [..] [a] serious, unmet clinical need. Broadly, subtypes of chronic itch have been delineated and termed pruriceptive, neuropathic, neurogenic, and psychogenic itch."

Pruriceptive itch follows activation of primary nerve terminals, is inflammatory in nature, and notably follows, not precedes, skin damage. A neuropathic-type itch stems from nerve injury or nerve trauma. The neurogenic type is an itch resulting from central nervous system activation without necessarily activating the sensory nerve fibers (e.g., internal injury results in external, physiological reaction). A psychogenic-type itch comes from underlying mental illness (as with delirium). So, an itch can be caused by something seemingly minor (skin irritation), injurious (nerve trauma), deceptive (overactive nerves), or systemic (internal injury or disease).